I had a look in the tank last night for a good 20 minutes, just me, them and a torch. I found not a single catfish. Today I decided to search for them in case of any living ones. I assumed that I had misjudged the butterfly and he had eaten them in the night.
I lifted up the log to see if there were any carcasses or anything. They were all underneath it hanging upside down grazing off them wood. They looked a bit like termites in rotting wood. I'm pretty sure all nine are still alive and they looked healthy too. They'd certainly been eating the pellets I'd laid out for them.
I'm not entirely sure where to go from here. I suppose there's not much I can do, perhaps when they feel more relaxed they'll journey out.

I'm very relieved they're all ok, I wouldnt forgive myself had I accidentally fed the catfish to the butterfly.
I've been doing some reading looking for a fish that can live in acidic-neutral waters, tolerate being kept in a group and won't nip the butterfly. They also have to be around 2-3 inches when full grown. If anyone knows of any such fish I'd be much obliged.
A few different species I've been thinking of are
5 dwarf gouramis - 1 male and 4 females. Are these known to be overly aggressive? Would I be better off to just get females? The main concern here is if they'll nip at the butterfly. I'm fairly certain that they're too big for the butterfly. If I get a large group will it be less likely to nip the butterfly?
Other gourami sorts - like pearls, honeys, sparklings or moonlights. Would I have to worry about sexes with these?
Apistogramma - I'm not sure what species are available or if they should be kept in harems or pairs. I'm guessing males won't get along too well.
Kribensis - Ive heard these can get nasty when breeding so if I go with them I'll probably only get one.
Keyholes - I'd love to have a keyhole or two. The problem is availability. I've not seen any for sale for ages.